REPTILES. 



95°, tlie whole mouth appeam yellow : the valve is elevated, 

 and the opening of the fauces is not fecn. If we furprife 

 him, the valve is generally deprcffed ; and if a pcrfon runs 

 the rifle of approaching fufficiently, a round body of a 

 beautiful red colour, which is the opening of the glottis, 

 jrvay be perceived. This valve enables the crocodile to 

 feize his prey under water without running the rifk of being 

 inundated by the great quantity of fluid that would pals 

 into the oefophagus. When he Iwallows, the valve mud 

 be deprefled, and the animal on dry ground. The os 

 hyoides of the crocodile of the Orinoco is a membranous 

 fpatula, broad, concave, and terminated by two fhort horns. 

 The OS hyoides of the Egyptian crocodile, as delijieated by 

 Mr.Duvernev, is altogether different from that of the South 

 American animal ; another proof ot the dillinftion between 

 the crocodiles of the old and new continent. In an animal 

 of eighteen feet, the tongue is twenty- five inches: it is 

 yellow, flelhy, and covers the wiiolc jaw ; but it is attached 

 on all fides, fo that the os hyoides cannot elevate it to the 

 end. The anterior or fpatula-fhaped portion of this bone 

 enters the membranous fubftance of the tongue, which it 

 can elevate at a right angle. As the fides and extre- 

 mity of the organ are fixed, this motion of the, bone can 

 only carry with it the membranous part of the tongue, 

 which forms the fold prefenting itfclf like an elevated valve. 

 The OS hyoides is depreffed, and the valve im.mediately dif- 

 appears. Three conditions are neceflary to the execution 

 of this meehanifm, a tongue attached to the lower jaw ; a 

 dudlile and flexible membrane covering it ; and an os 

 hyoides broad in front. The yellow fubftance in the ante- 

 rior part of the mouth belongs to the tongue as well as the 

 fold covering the entrance oi the oefophagus. Humboldt 

 found that the tongue fwelled very much, when fubjefted 

 to Galvanic influence, by means of zinc and filver. See 

 Recueil d'Obfervations d' Anatomic comparee e; Zoologie, 

 faites dans le Voyage de Humboldt et Bonpland, t. i. 

 pag. 9. pi. 4._ 



Geoffroy gives a fimilar defcription of the tongue, os 

 hyoides, and their meehanifm, in the Nilotic crocodile. He 

 defcribes it as a yellowifli, (hagreened fliin, exaftly like the 

 fubltance of the palate, pierced by numerous fmall holes, the 

 excretory dufts of the glands fituated on its upper furfuce, 

 and adhermg on all fides to the branches oi the lower jaw. He 

 fpeaks of the broad anterior part of the os hyoides forming, 

 by its elevation, a veil, which covers, all the back of the 

 mouth. Thus, the animal can remain under water with the 

 jaws open, and receive air through the nollrils, the only part 

 above the fnrface, without the water entering the throat or 

 trachea. Annales du Mufeum, vol. ii. p. 42, et fcq. 



Epiglottis. — In moll reptiles the opening of the glottis is 

 neither covered by a valve, as in the mammalia, nor armed 

 with papillre, as in birds. Yet a kind of epiglottis may be 

 obferved in the common igiuna, and in the Schneiderian fcink. 

 Tliere is a rudiment in tha crocodiles ; it does not appear in 

 feveral other animals of the lame order, nor in the chelonian, 

 ophidian, and batracian reptiles. The cylindrical larynx of 

 the dragon, and its fimple opening behind the root of the 

 tongue, are very well reprefented in Blumenbach's Abbil- 

 duiigen Natur-Hiftorifcher gcgenitande, N" 98. Is the 

 abfence of the epiglottis conntdled with the peculiar mo- 

 dification which refpiration undergoes in this clafs ? or 

 with their deglutition ? On the former point we may ob- 

 ferve, that, as they breathe only at confiderable intervals, 

 there is no danger of the glottis being opened during fwal- 

 lowing, and its edges may confequently be kept cloU'ly ap- 

 proximated. Again, as they fwallov? their food whole, it 

 is not likely to pafs into the larynx. 



Fauces. — The openings of the nollrils exc fituated very 

 forwards in reptiles, and are not clofed by any moveable 

 curtain, as in the mammalia. A kind of immoveable valve, 

 attached to the anterior edge of the opening, and leaving 

 the orifice free behind, may be fcen in the gecko fira- 

 briatus. 



There is fomething analogous to tlie velum palati in th^ 

 crocodile. The nollrils open far back, contrary to what 

 we have mentioned concerning other reptiles. They form 

 a round aperture in the moll diftaiit p.irt of the arch ot 

 the palate. The membrane lining this concavity forms 

 a loofe production a little in front of the opening in 

 queflion, which defcends on the fides, growing a Ettle 

 broader, until it meets another elevation behind the bafis of 

 the tongue. Thcfe form together, by their loofe edge, the 

 ifthmus faucium, or entrance of the throat. The firft af- 

 fords iome proteflion to the opening of the nollrils, but can- 

 not entirely clofe it ; the latter contributes, with the rudi - 

 ment of the epiglottis already mentioned, to cover the glottis. 



The entrance of the throat is large in all reptiles, and 

 capable, in many, of ilill greater fize, by the expanfion of the 

 lower jaws. There is nothing deferving the name of ilth- 

 mus. They fwallow entire animals, which cannot pafs into 

 the nollrils, and hence do not require a velum palati. 



Pharynx. — As the nollrils open forwards in reptiles, the 

 pharynx has not the fame relation to the nafal cavity, as in 

 the mammalia and birds. The mouth and larynx communi- 

 cate with it, and there is ufually a large aperture correfpond- 

 ing to the Euftachian tube. 



The pharynx can hardly be diftinguilhed from the com- 

 mencement of the cefophagus in reptiles. Their diameter is 

 ufually the fame ; and there is abfolutely no difference in the 

 afpeft of the membrane forming their internal parietes. It 

 prefents a great number of longitudinal folds, which arc 

 effaced when a prey of large fize is fwallowed. There is no 

 exterior mufcle enveloping the entrance of the canal. 



Deglutition maybe affilled, in the chelonians, by the aftion 

 of the ilerno-thyroidei, which relt on the oefophagus in the 

 whole length of the neck ; and even adhere in front to its 

 parietes, and to the part which may be regarded as belonging 

 to the pharynx. The os hyoides may alio contribute to de- 

 glutition, by means of the mufcles which elevate it. 



This office is particularly evident in the batracians, and 

 efpecially in the frogs and toads. The hyoideal plate, which 

 fupports in thefe animals the extenfive parietes of the back 

 of the mouth and palate, is put in motion by the mylo- 

 hyoideus and the mulcles analogous to the llylo-hyoidei, only 

 for the purpofe of elevating thefe pai'ietes, and applying 

 them to the concavity of the palate. There is alfo another 

 mufcle coming from the upper and back part of the head, 

 in front of that which correfponds to the Itylo-hyoideus ; it 

 is narrow at its origin, but expands as it pades forwards and 

 downwards, and as it covers that part of the throat which is 

 prominent behind. It is continued to the edge of the hyoi- 

 deal plate, in which it is inferted, its fibres adliering alfo to 

 the membrane of the throat, on which they lie. Their aftion 

 will elevate the hyoideal plate, and apply the membrane 

 which they cover to the oppofite furface of the cavity. 



The longitudinal fibres, belonging both to the pharynx and 

 oefophagus, are more or lefs ftrongly marked. 



CEfephagus and Stomach. — The former tube does not pre- 

 fent thofe dilatations which we notice in birds : it retains 

 nearly an uniform diameter throughout, or the change, if 

 any, is gradual. But this diameter is, in moll cafes, much 

 more confiderable, in comparifon with that of the ftomach, 

 than in the two preceding clafl'es. Under certain circum- 

 (lances, indeed, the cefophagus is larger than the (tomach 

 4 Y 7 in 



